Conventional medical devices and industrial devices photographing an object with X-rays have employed an X-ray tube assembly as an X-ray generation source. A rotating anode type X-ray tube assembly has been known as the X-ray tube assembly.
The rotating anode type X-ray tube assembly comprises a rotating anode type X-ray tube which emits X-rays, a stator coil, and a housing which accommodates the rotating anode type X-ray tube and the stator coil. The rotating anode type X-ray tube comprises a fixed shaft, a cathode which generates electrons, an anode target, a rotor, and a vacuum envelope. The rotor comprises a cylindrical portion and the like and is connected to the anode target. The rotor is supported to be freely rotatable to a rotation axis by bearings, and rotates with a magnetic field generated from the stator coil. As the electrons emitted from the cathode collide with the anode target, X-rays are emitted.
As the bearings, for example, dynamic pressure bearings using a lubricant with which a gap between the fixed shaft and the rotor are filled are used. If leakage of the lubricant occurs at employment of the bearings of this type, the lubricant may be short, the rotation speed of the rotor may become lower, and the rotor may be stopped.